1. Field of the Invention
The invention pertains generally to apparatuses and methods for treating a substrate with a fluid, i.e., a liquid or a gas.
2. Description of the Related Art
In the fabrication of a variety of devices such as, for example, printed circuit boards, various fluid treatments are applied to corresponding substrates, including rinsing, drying, chemical etching and electrolytic processing. These fluid treatments have been carried out using dip tanks and various configurations of spray nozzles and fluid jet injectors.
Dip tanks, while useful, are disadvantageous because they require an undesirably large amount of time for mounting and unmounting substrates to and from racks or baskets which are submerged within the dip tanks. In addition, mass transfer within a dip tank is typically effected via diffusion, which is often too slow a process to be economic. For example, when used for substrate rinsing, a dip tank quickly becomes heavily laden with the material to be removed from a substrate, which reduces the diffusion rate within the dip tank, and thereby slows rinsing. In fact, dip tanks often become so heavily laden with removed material that further rinsing becomes impossible.
Spray nozzles are disadvantageous because, among other reasons, they serve to atomize a fluid, resulting in the evaporation of the fluid. As a consequence, undesirable chemical emissions are exacerbated and re-use of the fluid is precluded, both of which are uneconomic. In addition, because the sprays produced by spray nozzles typically fail to achieve fluid bearing action on the substrates being processed, these substrates must be transported to and from the sprays by rollers and guides positioned between the spray nozzles and the substrates. However, the presence of these rollers and guides is undesirable because, among other reasons, they produce nonuniformities in the spray action which results in, for example, nonuniform rinsing and etching. Moreover, because sprays quickly lose momentum, they often fail to achieve efficient fluid treatment of specific substrate areas, which limits processing rate and throughput. For example, sprays are often inefficient or ineffective in rinsing or drying specific substrate areas, such as the interiors of holes in substrates, because whatever fluid reaches such areas tends to be retained on or in these areas (a phenomenon called dragout), with relatively little fresh fluid reaching these areas. Moreover, sprays often re-deposit or re-position, rather than remove, debris on the substrate, which then requires the use of additional sprays. Consequently, the use of sprays often requires the use of an undesirably large amount of processing area, which is also uneconomic. While attempts have been made to orient sprays to achieve directionality and thereby overcome some of the above-mentioned disadvantages, these attempts have typically been accompanied by a torque being imposed upon the subtrate by the directed spray. This results in instabilities in the motion of the substrate, often causing jamming of the substrate in the corresponding processing equipment, resulting in damage to the substrate or equipment, which is undesirable and counterproductive.
The use of fluid jets in the fluid treatment of substrates is potentially advantageous because fluid jets exhibit directionality and therefore, in principle, are capable of overcoming the disadvantages of sprays. However, previous configurations of fluid jets have failed to overcome the problem of dragout, particularly in the case of substrates with holes. Moreover, these previous fluid jet configurations have also imposed torques on substrates, resulting in undesirable and counterproductive instabilities in the motions of substrates.
Thus, those engaged in the development of fluid treatment apparatuses and methods have long sought, thus far without success, fluid jet configurations which: (1) overcome the problem of dragout, particularly in the case of substrates with holes; (2) avoid imposing torques on substrates; and (3) substantially reduce the need for rollers and guides for transporting substrates, thereby substantially reducing the interference caused by such rollers and guides.